Field of the Invention
The present invention relates to an evaporator with a cool storage function.
Discussion of the Background
In recent years, in order to protect the environment and improve fuel consumption of automobiles, there has been proposed an automobile designed to automatically stop the engine when the automobile stops, for example, to wait for a traffic light to change.
However, an ordinary car air conditioner has a problem in that, when an engine of an automobile in which the air conditioner is mounted is stopped, a compressor driven by the engine is stopped, and supply of refrigerant to an evaporator stops, whereby the cooling capacity of the air conditioner drops sharply.
As one measure to solve such a problem, imparting a cool storage function to the evaporator has been considered, to thereby enable cooling of a vehicle compartment by releasing the cool stored in the evaporator, when the compressor stops as a result of stoppage of the engine.
The present applicant has proposed an evaporator with a cool storage function of such a type (see Japanese Patent Application Laid-Open (kokai) No. 2012-42167). In the proposed evaporator, a plurality of flat refrigerant flow tubes which extend in the vertical direction and whose width direction coincides with an air-passing direction are disposed between a pair of tanks spaced from each other in the vertical direction such that the refrigerant flow tubes are spaced from one another in the thickness direction thereof. The evaporator has spaces each formed between adjacent refrigerant flow tubes. Cool storage material containers contains a cool storage material are disposed in some spaces, and fins are disposed in the remaining spaces. Each cool storage material container has a container main body portion joined to the corresponding refrigerant flow tubes, and an outward projecting portion which extends from the leeward edge of the container main body portion over the entire length thereof in the vertical direction and which projects beyond the refrigerant flow tubes with respect to the air-passing direction. The outward projecting portion of each cool storage material container has an expansion portion which is expanded leftward and rightward in relation to the container main body portion and which has a dimension (measured in the left-right direction) greater than those of the container main body portion and the outward projecting portion. Each of the fins disposed in the spaces located adjacent to the space in which the cool storage material container is disposed has a fin main body portion joined to the corresponding refrigerant flow tubes, and an outward projecting portion which projects from the leeward edge of the fin main body portion and which projects beyond the refrigerant flow tubes with respect to the air-passing direction. The outward projecting portions of two fins are in contact with and are brazed to the outer surfaces of left and right side walls of the expansion portion of the outward projecting portion of the corresponding cool storage material container.
The evaporator with a cool storage function disclosed in the publication operates as follows. In an ordinary cooling period in which a compressor is operating, the cool carried by the refrigerant flowing through the refrigerant flow tubes is transferred to the cool storage material within each cool storage material container and is stored in the cool storage material. Meanwhile, when the compressor stops, the cool stored in the cool storage material within each cool storage material container is transferred to the fins disposed in the corresponding spaces through the refrigerant flow tubes to which the container main body thereof is brazed. Subsequently, the cool is released from the fins to air flowing through the spaces.
Incidentally, in general, a paraffin-based latent heat storage material whose melting point is adjusted to 3° C. to 10° C. is used as a cool storage material which is charged into cool storage material containers of an evaporator with a cool storage function of such a type.
Also, the strength of each cool storage material container is determined such that the cool storage material container does not break within an ordinary range of temperature of an environment in which the evaporator is used (hereinafter referred to as an “ordinary use environment temperature range”) (e.g., within a range of −40° C. to 90° C.) even when the density of the cool storage material in the liquid phase changes and the air remaining in the cool storage material container thermally expands with a resultant increase in the internal pressure. However, if the ambient temperature becomes higher than the ordinary use environment temperature range, the change in the density of the cool storage material in the liquid phase and the thermal expansion of the air remaining in the cool storage material container become remarkable. In such a case, depending on a cool storage material charging ratio (the ratio of the volume of the charged cool storage material to the internal volume of the cool storage material container), the cool storage material container may break due to the internal pressure, and as a result, the refrigerant flow tubes may break. In particular, since the cool storage material container is composed of a container main body portion which is brazed to corresponding refrigerant flow tubes and an outward projecting portion to which corresponding fins are brazed, even when the internal pressure increases abnormally, the cool storage material container is unlikely to deform so as to absorb the increase in the internal pressure, and the breakage of the cool storage material container due to the internal pressure is more likely to occur.
In addition, in the evaporator with a cool storage function disclosed in the above-mentioned publication, each of the cool storage containers and the fins has an outward projecting portion which is formed over the entire length (in the vertical direction) such that the outward projecting portion projects beyond the refrigerant flow tubes, and the outward projecting portions of the corresponding fins are brazed to the outer surfaces of left and right side walls of the expansion portion of the outward projecting portion of each cool storage material container. Therefore, the size becomes relatively large, and the weight increases. Also, the cool storage material within each cool storage material container is effectively cooled at portions of the cool storage material container which are brazed to the corresponding refrigerant flow tubes. In the evaporator with a cool storage function disclosed in the above-mentioned publication, since the outward projecting portion of each cool storage material container is not brazed to the refrigerant flow tubes, the outward projecting portion is inferior to the container main body portion in terms of the effect of cooling the cool storage material within the cool storage material container. Since the outward projecting portion is provided over the entire length of the cool storage material container in the vertical direction, the conventional evaporator has a problem in that the amount of the cool storage material not cooled effectively increases.
In order to solve the above-mentioned problem, the present applicant has proposed an evaporator with a cool storage function which can prevent breakage of cool storage material containers due to an abnormal increase in the internal pressure (Japanese Patent Application Laid-Open (kokai) No. 2012-137199).